The field of this invention is injection molding, particularly plastic injection molding. In plastic injection molding a key problem is involved with the cost of the molds. The fewer molds that are required to sustain the necessary level of production the more cheaply the product may be produced and sold. There is a direct relationship, therefore, between the length of mold cooling time and the number of molds needed. One of the means of accomplishing rapid mold cooling is described in my co-pending application Ser. No. 07/193,728 wherein I describe the arcuate and spherical disbursement of core pins made from a copper alloy and used, whether or not there is a need for an indentation or aperture in the mold, to dissipate heat from the mold more rapidly thereby diminishing time consumed in using any one mold.
Where the injection nozzle is inserted into the mold a sprue bushing is adapted for the mold to receive the nozzle snugly leaving as little a "tail" or sprue as it is called in the industry as is possible. This bushing, of course, heats up as a result of the molten plastic flowing through it into the mold, and as a result of receiving the hot nozzle. When the flow of molten material through the nozzle is discontinued the bushing and "tail" or sprue must also cool before the mold may be said to be cured or cooled to the point of being able to discharge its product without damage.
Finally, the sprue or tail of the product being molded must be smallest in cross-sectional dimension at the orifice of the injection mold nozzle and largest at the end of the elongated bushing remote from the nozzle to facilitate ready discharge of the cooled molded product from the mold. In other words the cross-sectional dimension and shape of the sprue is of significant concern to the speed of the process.